1. Field of the Invention
This invention relates to a floating tool holder.
2. Prior Art
U.S. Pat. No. 3,595,591 discloses two floating tool holders, one of which has a deep-hole capacity and the other of which has centering means. The deep-hole capacity enables a substantial portion of the tool to be inserted in the tool holder to minimize the amount that the tool projects therefrom. The centering feature restores or tends to maintain a tool chuck assembly concentric with the axis of rotation. Although these prior devices are advantageous, they have certain disadvantages. One of the main disadvantages is that these prior devices employ balls to carry substantial thrust loads. Such axial loads create brinelling at the balls, thus impairing the ability of the tool chuck assembly to float in a radial direction. Another difficulty with these prior art devices is that they employ a seal between the tool chuck assembly and a radially adjacent flange. Such seal is resilient and must yield whenever there is any floating movement of the tool chuck assembly. Although this constitutes a tendency to provide self-centering, it could be expected that the centering force is too great or too little, thus impairing the quality of workmanship that can be performed. Similarly, the self-centering means of this prior patent also may provide a centering force that is too great or too little. With a heavy tool being driven, a somewhat greater centering force is needed than if a lightweight tool were used. Further, these prior constructions have a greater axial length than is desired. Various solutions have been proposed by others for one or more of these problems, particularly the brinelling problem, and those prior devices have been difficult in that they are susceptible to breakage under heavy torque and are costly to produce. Some of these problems are at their worst when the tool holder is used with an end reamer. Thus the main problem is to maintain the reliability of floating action even though the tool holder is used with a substantial end thrust during cutting.